NEETBotanyCell - The Unit of Life
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The two subunits of an 80S eukaryotic ribosome are 50S and 30S. Reason (R): The Svedberg's unit ('S') stands for the sedimentation coefficient, which indirectly is a measure of density and size. In the light of the above statements, choose the correct answer from the options given below:
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
D. (A) is not correct but (R) is correct
Step-by-step solution
Assertion (A) is incorrect because the two subunits of an 80S eukaryotic ribosome are 60S and 40S, not 50S and 30S (which are the subunits of a 70S prokaryotic ribosome). Reason (R) is a correct statement as per NCERT. 'S' stands for Svedberg's unit, which represents the sedimentation coefficient and indirectly measures the density and size of the ribosomal particles. This non-additive physical property explains why the subunits (e.g., 60S and 40S) do not arithmetically add up to the total ribosome value (80S). The